I replaced my windshield wiper motor. After I checked that the motor works I put the wiper arms on and it quit working. I checked the nuts that hold the arms on, then I took it all apart and put it back together again. I had to be sure it was not an error on my part. The same thing happened. Actually I only need to put one arm on for it to stop working. You can hear the motor working it just does not seem to be able to move the arms. When I take them off it works again. Before I had to replace the motor, every once in a while the wipers would not turn off until I turned the motor off.
Thank you for any help. DN

First question is about what happened to the original wiper motor and why you replaced it? The next question is about where / what brand of replacement you bought?

That said, the wiper motor gose through the BCM (Body Control Module) so there may be wacky / unrelated issues but we can get back to that if there's still a problem. What I would do is double check for good connections and good grounds before condeming the motor. IOW, you may have a voltage drop under load, especially if the cowl area was filled with water on a regular basis. (probably the number one reason for failure around here) While we are on that topic be sure to pull the two drain hoses and blow them clear. I do mine at every oil change but since my neighbor cut down his pine trees it's been less of a problem. (just an example of what you may find in there)

Anyway, back to the connections.... make sure both the ground on the harness and the muti-prong plug for the motor are not cruddy. If necessary you can clean things up and apply a small bit of grease on reassembly to retard future issues.

BTW, if that was a remanufactured motor it may be marginal... but I would double check the above before getting another one. Also, fully support the little arm on the motor if you need to switch it between the old and the new. If you don't then you may strip the internal gears while working the nut, which may be the problem you have now.